GM ECM injector driver capacity

[Ken Kelly]

>  You may be able to run the ECM all day
> >> >with the resistors, and still blow it up the first time you
> >> >stick the inductive load on it.
> >>

> >
> Just being dumb here, but why would increaseing the load raise
> the back EMF,  I can understand having a higher current load to deal
> with, since the higher switching currents, but the voltages should be
> close eh?.
> Cheers
> Bruce

Bruce,
	If you put a voltage waveform like a square wave across a resistor, the current
waveform will exactly track the voltage waveform with a current = voltage
divided by resistance relationship.

	When you do the same thing with an inductor the results are much more complex.
The inductance introduces a time delay between the between the voltage and
current waveforms, but more importantly the inductor actually sets up a magnetic
field around the coil. When you remove the original voltage the magnetic field
collapses and the inductor actually generates a voltage spike of it own. The
driver in the ECM or a diode wired across the driver has to absorb this spike.
The more injectors that are hooked up to the driver, the more power it must
absorb.

	When the inductive device has moving parts like an injector, the moving parts
actually store energy that is released when the injector is turned off. In fact
the Injector solenoid acts like a small generator, increasing the amount of
energy the driver must absorb.

		Ken